DProf output of named functions.

[regexes]

Fellow Monks,

I have a simple program which parses an XML file and does "stuff". I use it on different OSes.

I have read the profiling tutorial here: Profiling your code.

I'm having a problem understanding why some of the output under Name differs between OSes, i.e. the functions differ. I would have thought they would be the same. I'm confident that someone here can explain the error in my thought process. ;-)

Take the following... (I've cut it to show only the relevant part..)

On AIX

                    
Total Elapsed Time = 1.292316 Seconds        
User+System Time = 0.282316 Seconds            
Name
XML::SAX::PurePerl::Reader::URI::new
XML::SAX::PurePerl::BEGIN
main::BEGIN
XML::Simple::find_xml_file
main::ParseFile
XML::SAX::PurePerl::Productions::BEGIN
strict::bits
Encode::BEGIN
XML::SAX::ParserFactory::BEGIN
XML::SAX::PurePerl::Reader::URI::BEGIN
File::Temp::BEGIN
XML::Simple::start_element
XML::Simple::XMLin
XML::SAX::PurePerl::Name
XML::SAX::PurePerl::CharData

Just looking at the XML function calls produces this list:

XML::SAX::PurePerl::Reader::URI::new
XML::SAX::PurePerl::BEGIN
XML::Simple::find_xml_file
XML::SAX::PurePerl::Productions::BEGIN
XML::SAX::ParserFactory::BEGIN
XML::SAX::PurePerl::Reader::URI::BEGIN
XML::Simple::start_element
XML::Simple::XMLin
XML::SAX::PurePerl::Name
XML::SAX::PurePerl::CharData

This is what I don't understand... why are there some function calls being performed on some OSes but not on others? Or are some irrelevant enough that they are simply not being listed?

on Linux_x86_64

XML::SAX::PurePerl::BEGIN
XML::SAX::Base::get_feature
XML::SAX::ParserFactory::_parser_class
XML::SAX::BEGIN
XML::SAX::ParserFactory::BEGIN
XML::SAX::PurePerl::Reader::BEGIN
XML::SAX::PurePerl::Reader::URI::BEGIN
XML::SAX::PurePerl::doctypedecl

on Solaris 10

XML::SAX::PurePerl::BEGIN
XML::SAX::PurePerl::skip_whitespace
XML::SAX::PurePerl::Reader::data
XML::Simple::start_element
XML::SAX::PurePerl::Reader::Stream::move_along
XML::SAX::PurePerl::element
XML::SAX::PurePerl::Productions::BEGIN
XML::Simple::BEGIN
XML::SAX::ParserFactory::BEGIN
XML::SAX::PurePerl::Reader::BEGIN
XML::SAX::PurePerl::Reader::URI::BEGIN

I would have thought the output of DProf on the XML::Simple module would be identical on each OS. Why is this not so?

Can someone enlighten me please?

regexes

[kyle]

why are there some function calls being performed on some OSes but not on others? Or are some irrelevant enough that they are simply not being listed?

It's the latter. By default dprofpp will list only the top 15 function calls.

I normally wouldn't expect profiling results to be exactly the same across architectures for several reasons.

1. Profiling results can vary from run to run as it is.
2. The timings are based on user+system time. User time is the time spent in your code and system time is the time spent in the OS serving your code. When you open and read a file, for instance, the OS is doing that work, and the time it spends doing that counts as system time. Each OS might spend different amounts of time on the same calls based on differences between them.
3. Each OS may have its own limits on how well it can measure time at all (i.e., precision, granularity). Compounded measurement errors could be skewing results.
4. Without seeing the code, I don't know, but it's possible that there is some branching according to OS. I don't know why that would be the case for you, but it's certainly possible in general.

[djp]

5. Underlying compilers, libraries, instruction sets, and hardware.

[perrin]

You probably have different versions of DProf and Perl on these machines.